In the medical arts, one of the more commonplace devices is the hypodermic syringe which is used to inject a quantity of fluid beneath the skin of a patient. While the structures of such hypodermic syringes vary with design choice, all generally include a cylindrical barrel defining a central cylindrical bore which terminates at one end in a restricted passage in communication with an outwardly extending hollow pointed needle. The remaining end is generally open and receives a piston assembly which includes an elongated driver supporting a piston. The piston is sized to sealingly slide within the bore of the syringe barrel and thereby control the volume confined within the interior of the syringe bore between the end needle passage and the piston.
In typical use, the needle is inserted into a small container after which the piston driver is drawn outwardly from the syringe barrel moving the piston away from the needle passage and drawing a quantity of the to-be-injected fluid into the syringe bore. Thereafter, the needle is withdrawn from the container and the syringe is pointed upwardly. The piston driver is then moved into the syringe bore a short distance to expel any trapped air from the syringe interior making the syringe ready for use. As a final step, the needle is inserted into or beneath the skin of the patient and the driver is moved inwardly within the syringe bore to expel the desired quantity of fluid into the patient's system. Finally, the needle is withdrawn from the patient's skin and discarded.
While syringes manufactured and used by the medical profession today are generally intended for a single use, in fact their structures are often sufficiently sturdy to facilitate multiple use by persons obtaining them through various unauthorized means. Most prevalent among such unauthorized users of hypodermic syringes are intravenous drug users who often use such syringes repeatedly and in many cases exchange syringes with fellow intravenous drug users.
While a problem of infection and disease proliferation has usually accompanied such unauthorized use of syringes by intravenous drug users, the recent increase in the disease known as Acquired Immune Deficiency Syndrome (AIDS) has greatly increased the alarm of the medical profession at such unauthorized use of discarded syringes.
Through the years, a number of hypodermic syringes have been developed which are directed to increasing the safety of use of hypodermic syringes. One such device is set forth in U.S. Pat. No. 3,306,290 issued to Weltman which sets forth an AUTOMATICALLY RETRACTABLE NEEDLE SYRINGE having an elongated tubular body defining a central bore and a slidable piston assembly therein. A hub mounted on the body portion defines an axial bore, receives the needle portion of the syringe and provides a safety member therefor.
U.S. Pat. No. 4,258,713 issued to Wardlaw sets forth an AUTOMATIC DISPOSABLE HYPODERMIC SYRINGE in which a disposable syringe includes a retracted needle which is driven by a spring to administer an injection. The needle is contained within a housing and is driven from the housing to administer the injection. A release mechanism is provided to operate the syringe.
U.S. Pat. No. 4,188,950 issued to Wardlaw sets forth a DISPOSABLE SYRINGE in which provisions are made for rendering the needle incapable of harming anyone once the unit is discarded. The syringe operates with a retracted needle which is driven to a protruding position when the device is used. After use the needle is retracted from the protruding position and is bent to prevent the needle from harming anyone and to prevent reuse of the needle.
U.S. Pat. No. 4,139,009 issued to Alvarez sets forth a HYPODERMIC NEEDLE ASSEMBLY WITH RETRACTABLE NEEDLE COVER in which a disposable hypodermic needle assembly includes a permanently attached but retractable covering means for the forward portions of the needle. The covering means include an annular slide member slidable with respect to the needle and normally positioned to cover the forward or pointed portion of the needle. A plurality of elastically resilient arms support the slide member in the covering position but may be withdrawn therefrom by sliding the slide member down the needle shaft and overcoming the elasticity of the resilient arms. Once the needle is used, the resilient arms return the slide member to the covering position and means are provided for locking the slide member in the covering position.
U.S. Pat. No. 4,507,117 issued to Ryan, et al. sets forth a SYRINGE APPARATUS WITH RETRACTABLE NEEDLE in which a syringe apparatus includes a syringe barrel and internal movable piston as well as an extending needle portion in communication therewith. A first locking member locks the needle in the extended position while a second locking member locks the needle to the slidable piston within the syringe barrel. In use, the needle is initially locked in the extending position and injection is administered. Thereafter, the needle may be unlocked from the extended position and retracted into the barrel by locking the needle to the piston and drawing the piston inwardly pulling the needle into the barrel interior.
U.S. Pat. No. 4,378,015 issued to Wardlaw sets forth an AUTOMATIC INJECTING SYRINGE in which a hypodermic needle employs a retracted needle contained within the syringe housing. The syringe is fabricated from a minimum number of parts and is intended to be inexpensively and easily assembled. A safety feature is included which prevents accidental operation of the syringe.
While the foregoing described prior art devices provide some protection and increased safety of the use of hypodermic syringes and some prevention of the reuse thereof, they often render the hypodermic syringe more costly to manufacture and more cumbersome to use. In addition, several of the prior art structures, such as those described above intended to render the hypodermic syringe limited to a single use, require a special action on the part of the medical professional to assure the non-reuse of the hypodermic syringe. The need for additional manipulation of the syringe to render it incapable of further use imposes an undesirable burden on the medical professional and raises the possibility of reusable syringes being available.
There remains, therefore, a need in the art for a convenient to use, inexpensive to manufacture hypodermic syringe which is limited to a single use. There remains a further need for such a single use syringe which is automatically rendered inoperative following its normal use by the medical professional.